Understanding the ultra-high energy regime of string theory has been long sought-after, especially after the work of Gross and Mende [1]}, [2]} who found substantial simplifications in string scattering in this domain. This is the regime explored by the tensionless limit of string theory, where the worldsheet of the string becomes null and the worldsheet metric becomes degenerate. In this limit, the worldsheet conformal symmetry is replaced by BMS\(_3\) , which now arises as residual symmetries of the tensionless worldsheet [3]}, [4]}. So the theory of tensionless strings is organised by this underlying BMS algebra in the same way as usual string theory is dictated by worldsheet conformal invariance [5]}. This is thus another very important place where two dimensional BMS invariant theories play a pivotal role It is of interest to note here that some rather unique phenomena in the quantum tensionless strings have been recently unearthed [6]}, [7]}, [8]}, a lot of which is based on a better understanding of the underlying BMS algebra.. It is important to stress here that the BMS symmetries that arise here are gauge symmetries, as opposed to the case of putative dual theories to flatspace, where BMS symmetries are global symmetries of the field theory.
